#include <bits/stdc++.h>
using namespace std;
int k;

int main() {
    cin >> k;
    int s1 = 0;
    int s2 = 1;
    int s;

    if (k == 1) {
        cout << 1;
        return 0;
    }

    for (int i = 2; i <= k; i++) {
        s = s1 + s2;
        s1 = s2;
        s2 = s;
    }
    cout << s;
    return 0;
}